Vascular introducer sheaths are well known components of vascular access systems which are used in a wide variety of diagnostic and therapeutic vascular procedures, such as angiography, angioplasty, thermolysis and embolization procedures. Vascular access systems typically include an introducer sheath for use in combination with a guide wire and a dilator. The introducer sheaths usually include a hemostatic or hemostasis valve which inhibits blood loss as guide wires, catheters and the like are introduced and manipulated in the vasculature via the sheath.
An example of a known hemostasis valve is disclosed in U.S. Pat. No. 5,520,655 to Davila et al. Davila '655 discloses a hemostasis valve including an inner housing, an end cap and a valve partition disposed between the inner housing and the end cap. The end cap includes a compression ring having a diameter which is less than the diameter of the valve partition but greater than the diameter of the aperture in the end cap and the bore in the inner housing. With this arrangement, the compression ring causes the valve partition to bow outwardly. Purportedly, the bowing enhances the sealing of the slit in the valve partition. However, the compression ring creates stress concentration points on the valve partition that may compromise the integrity of the valve partition. Furthermore, an excessive amount of compression must be applied by the compression ring against the valve partition to impart the bowing effect.
A similar hemostasis valve is disclosed in International Patent Publication No. WO 99/06099 to Paul. Paul '099 discloses a hemostatic valve including a gasket seal contained in a valve body and compressed therein by a cap connected to the valve body. The valve body includes a valve seat, which in turn includes a flange and a series of annular recessed steps. The flange serves to impart a concave shape to the gasket seal. The series of annular steps serve to prevent the gasket seal from being displaced. As with the hemostasis valve disclosed in Davila '655, the hemostasis valve disclosed in Paul '099 suffers from the creation of stress concentration points imparted by the flange onto the valve gasket. The annular steps recessed in the valve body, depending on the size, may also create stress concentration points on the gasket seal. These stress concentration points may compromise the integrity of the gasket seal and also require an excessive amount of compression to impart the desired curved shape of the gasket seal.